Add method for insider roster

[eshgovil]

Describe the problem
There currently exists no method to access the insider roster available on the site, next to the holders, e.g. https://finance.yahoo.com/quote/MSFT/insider-roster?p=MSFT

Describe the solution
Like the Holders class, implement one for InsiderRoster.

Additional context

Here is how I am hacking it for now:

def get_insider_roster(ticker: yf.Ticker, proxy = None) -> pd.DataFrame:
    url = f'https://finance.yahoo.com/quote/{ticker._data.ticker}/insider-roster'
    resp = ticker._data.cache_get(url, proxy)
    insiders = pd.read_html(resp.text)
    insiders = insiders[0].iloc[:-1]
    return insiders

[ValueRaider]

You could just submit a pull request, that's basically the code just convert columns to sensible types. Read #1084

[sshcli]

@eshgovil I agree this feature is needed.
I also would like to suggest adding Insider Transactions as well.
@ValueRaider Please let us know if this already exists. I can't find the way to get any insider information

[ValueRaider]

@sshcli Code and pull requests are public record, have a look.

[sshcli]

@ValueRaider Got it. Thanks.

[bot-unit]

@ValueRaider Close, please. Implemented at #1772